Stabilized bitumen compositions

ABSTRACT

Two or more different polymeric materials are stably incorporated into bitumen by effecting steric stabilization of a polyolefin, such as polyethylene, and by dispersing the other polymer, such as a styrene-butadiene-styrene copolymer, an ethylene-vinyl acetate copolymer or an EPDM copolymer in the stabilized polyethylene-bitumen composition. The ability to incorporate different polymeric materials in bitumen permits desirable modifications to the properties of the composition to be effected. In addition, different properties can be attained by modifying processing parameters.

REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase filing under 35 USC 371 fromPCT/CA94/00174 filed Mar. 28, 1994.

The present invention relates to the provision of stable dispersions ofpolymeric materials in bitumen for a variety of applications and methodsof producing the same.

BACKGROUND TO THE INVENTION

The combination of two or more polymer types into bitumen is considereddesirable from the standpoint of obtaining improvements in propertiesthat may not be possible with a single modifier. By providing a blend ofthe two or more types of polymers, it is conceivable that improvement inproperties can be achieved over a greater range of expectedpavement-service conditions.

While this goal is highly desirable, heretofore it has been difficult toachieve this result because of the inherent incompatibility of bitumenand the polymeric materials to be incorporated therein. In addition,different polymers, which, when used independently, are compatible withthe bitumen, in combination, interfere with the compatibility of eachother and/or the final system.

Various procedures have been attempted to improve the compatibility ofbitumen and polymers, for example, by the use of low molecular weightcopolymers, process oils, and by the use of specific processingconditions to promote chemical reactions, such as cross-linking.

In International patent application no. WO 93/07219 (corresponding toU.S. Ser. No. 863,734 filed Apr. 6, 1992), assigned to The University ofToronto Innovations Foundation, there is described the stabilization ofdispersed polyethylene and other olefin polymers in bitumen forimparting improved properties to such asphalt. The polyethylene ismaintained in a dispersed state by using a steric stabilizer which isanchored to the dispersed particles and which is compatible with theliquid medium. Such an arrangement maintains the dispersed polyethyleneparticles spaced from each other in the bitumen, and inhibits separationof the particulate phase from the liquid phase by the progressivecoalescence of dispersed particles.

In particular, a stable dispersion of polyolefin particles in bitumenmay be formed by employing a functionalized diene rubber which iscovalently bonded to a functionalized polyethylene, with or withoutliquid polybutadiene. Cross-linking of the unsaturated structure in thefunctionalized butadiene molecular chain to the bitumen forms anextended polybutadiene-based network with a partially cross-linkedstructure anchored to each of the polymer particles by compatibility ofthe functionalized polyethylene with the polymer particles and swollenby the bitumen phase, to provide a gel envelope about the polymerparticles, which prevents coalescence of the polymer particles.

SUMMARY OF INVENTION

It has now been surprisingly found that a wide range of copolymers maybe incorporated into the bitumen composition containing stabilizedpolyethylene or other polyolefin described in WO 93/07219 and suchcopolymer resists separation from the bitumen. The present invention,therefore, permits two or more different polymeric materials to beincorporated into bitumen and to remain stably dispersed therein.

Accordingly, in one aspect of the present invention, there is provided abitumen composition, comprising bitumen, at least one polyolefinsterically stabilized in the bitumen, and at least one additionalpolymeric material stably incorporated into the composition.

These stable novel bituminous compositions permit improved performanceand a versatility of formulation design which has not previously beenpossible, while also providing for compositions from which the polymercomponents do not separate.

In addition, it has been found that a wide variety of properties may beachieved, independent of the formulation utilized, depending on thesequence of addition of the polyolefin, copolymer and stabilizer to thebitumen and variations in other processing parameters, such as mixingtime, temperature and rate of shear.

In accordance with a further aspect of the present invention, there isprovided a method of forming a bituminous composition, which comprisesdissolving a functionalized diene in a solvent which is bitumen or anoil compatible with bitumen, dispersing a functionalized polyolefin inthe solvent, reacting the functionalized polyolefin and thefunctionalized diene so as to bind one end of the olefinic polymer tothe diene, dispersing a polyolefin in a molten form in the solvent,dispersing at least one additional polymer in particulated form in thesolvent to provide, in the bituminous composition, steric stabilizationof the polyolefin by bonding of the free end of the functionalizedpolyolefin to the particulate polyolefin and stable incorporation of theat least one additional polymer by entanglement, physical entrapment,chemical cross-linking or a combination of two or more of suchmechanisms, and where the solvent is oil compatible, dispersing theresultant composition in bitumen.

GENERAL DESCRIPTION OF INVENTION

The term "bitumen" used herein has its conventional technical meaningand means a class of black or dark-colored (solid, semi-solid orviscous) cementitious substances, natural or manufactured, composedprincipally of high molecule weight hydrocarbons of which asphalts,tars, pitches and asphaltites are typical. The term "asphalt" as usedherein has its conventional technical meaning and means a dark, brown toblack, cementitious material, solid or semi-solid in consistency, inwhich the predominant constituents are bitumen that occur in nature, assuch, or are obtained as residue in petroleum refining. The bituminousmaterial employed herein may arise from a variety of sources, includingstraight and vacuum residue, mixtures of vacuum tower wash oil, paraffindistillate and aromatic and naphthenic oils. Other asphaltic materials,such as rock asphalt, naturally-occurring asphalt and coal tar pitch,also may be used.

As described above, the present invention enables two or more differentforms of polymeric materials to be stably incorporated into bitumen inorder to expand the useful temperature range of the bitumen composition.One polymer component of the composition comprises a polyolefin, whichis preferably polyethylene, but may comprise other olefin homopolymersand copolymers of ethylene and other.olefin monomers. Such polyolefin ormixture of two or more polyolefins, is stably incorporated into thebitumen in the form of a particulate phase dispersed in the bitumen bythe mechanism of steric stabilization, as fully described in WO93/07219, referred to above. As described therein, a bifunctional orbicompatible molecule is employed which has one component bonded to thepolyolefin and another component soluble in the bitumen.

As described in WO 93/07219, the polyolefin component of the compositionpreferably comprises polyethylene. Such polyethylene may comprise lowdensity, linear low density or high density polyethylenes and maycomprise polyethylene blends, such as are obtained in pelletized, flakedor powdered recycled material. In general, dispersion of the polyolefincomponent is effected with the bitumen above the melting point of thepolyolefin, generally from about 100° to about 250° C., preferably about130° to about 200° C., for a time sufficient to form a stablecomposition, which may be about 0.1 to about 3.5 hours, usually about0.25 to about 1 hour.

One or more additional polymers are incorporated into such composition.Such polymers are generally copolymers and may contain residualunsaturation. Such copolymers are often incompatible with bitumen andhence normally separate or coalesce rapidly when stirring of thecomposition is stopped. However, in accordance with the invention, whensuch copolymers are incorporated into the stabilized polyolefincompositions, they become stabilized-and resist separation from thebitumen. Some copolymers which can be employed herein are alreadysomewhat compatible with bitumen or can be rendered so by suitableprocessing. The presence of the dispersed polyethylene phase inbituminous compositions comprising such materials at worst does notdestabilize such materials and frequently may improve such stability.

The manner in which the copolymers become stabilized in the compositiondepends on the nature of the polymer employed, and may includeentanglement, physical entrapment, chemical cross-linking orcombinations of two or more of such mechanisms.

Copolymers which may be incorporated into the bituminous compositionsaccording to the invention include elastomeric copolymer, including:

styrenic copolymers, such as styrene-butadiene rubber (SBR),styrene-butadiene-styrene block copolymers (SBS),styrene-ethylene-butadiene-styrene block copolymers (SEBS) andstyrene-isoprene-styrene block copolymers (SIS);

olefinic copolymers, such as polypropylene copolymers, ethylene-vinylacetate copolymers (EVA), ethylene methylacrate copolymers (EMA) andethylene propylene diene copolymers (EPDM).

other polymers, such as nitrile-butadiene rubber (NBR),polyvinylchloride (PVC), polyisobutene, and polybutadiene (PB).

Mixtures of two or more of such polymers may be incorporated into thebituminous compositions along with the polyolefin. The compositions ofthe invention may but do not necessarily employ components, such asprocess oils, which render the polymers more compatible with thebitumen.

In general, the choice of the polymer to be incorporated into thebitumen is influenced by the following parameters, as well as possiblyothers:

the asphalt chemical composition

the molecular weight of the asphalt

the molecular weight of the polymer(s)

the shear force applied during mixing of the components

the ratio of constituents of the copolymer, such as the mole ratio ofE:VA in EVA

The polymeric materials may be present in the bitumen composition in theform of particle dispersions, strand-like dispersions, solutions andcombinations in which the (co)polymer(s) is stabilized againstseparation.

In general, at low polymer loadings, the bitumen comprises a continuousphase in which the polymer is dispersed. However, at higher polymerloadings, a phase inversion may occur, whereby the polymer becomes thecontinuous phase.

One effect which has been observed in connection with the compositionsof the invention is that, by employing such copolymers in conjunctionwith the stabilization system described in WO 93/07219, a decreasedamount of copolymer material is required to achieve comparablemodification to the properties of the bitumen. For example, about 2.5wt. % of SBS is sufficient to provide the same elastic recovery asbitumen not having the stabilization system hereof to which about 4 wt.% SBS is added, thereby achieving a considerable cost saving withrespect to the copolymeric component.

In addition, as can be seen from the specific Examples below, it hasbeen found that the viscosity and other properties of the modifiedbitumen can be varied for the same or essentially the same quantities ofthe same components, depending on the order of mixing of the componentsin formation of the bitumen composition. The compositions of the presentinvention may be utilized in a wide variety of applications as a resultof the diversity of properties achieved by employing differentcompositional components and mode of formation.

The various alternative procedures of order of mixing and composition ofcomponents may be employed with other copolymer components as well aswhen such copolymer components are omitted and/or when polyethylene isomitted, for example, where two or more copolymers are stabilized.

Rather than form a concentrate in bitumen as described above, aconcentrate may be formed in oil or other medium and the concentrate inthis form may be introduced to the bitumen, along with the polymerand/or copolymer components.

Within the context of this invention, the manner by which the finaldispersion is achieved varies according to the nature of the copolymersand/or homopolymers and the process conditions employed. Depending onthe application to which the bitumen composition of the invention is tobe put, the quantities of polyolefin and of copolymer incorporated intothe bitumen may be varied widely. Preferably, the amount ofpolyethylene, when present in the composition, may vary from about 0.5to about 20 wt. % while that for the copolymer, when present in thecomposition, may vary from about 0.5 to about 20 wt. %. For example,with SBR and SBS copolymers, added to impart elasticity, the amount ofcopolymer employed may range from about 1 to about 15 wt. %.

In addition to these components, there may also be incorporated into thebituminous composition or dispersed phase comprising dissociated rubbervulcanate network, particularly prepared from scrap crumb rubber, suchas automobile tyre crumb rubber, as fully described in Internationalapplication PCT/CA93/00562 filed Dec. 29, 1993, in the joint names ofourselves and University of Toronto Innovations Foundation.

The stabilized bitumen compositions of the present invention also may beincorporated into other systems. For example, the stabilized bitumencompositions may be incorporated into the manufacture of rubber andplastic compounded compositions, such as in an amount of about 5 toabout 50 wt. %. Alternatively, the stabilized bitumen compositions maybe provided in the form of emulsions, with the continuous phase beingaqueous or organic. Masterbatch compositions comprising bitumen andstabilized polymers may be compounded with fillers and/or polymers andthe compounded composition may be pelletized to produce a pelletizedcomposition for subsequent incorporation into compositions for a varietyof industrial uses. The compositions described herein may be utilized ina variety of asphalt applications, including all types of paving,preformed paving bricks, roofing membranes, shingles, waterproofingmembranes, sealants, caulks, potting resins and protective finishes.

In one embodiment of the invention f or dispersion of the polyethylene,maleinized polyethylene, liquid polybutadiene (as required),amino-terminated poly (butadiene-co-acrylonitrile) or amino-terminatedpolybutadiene and elemental sulfur may be dispersed in bitumen. For aconventional hot mix asphalt paving application, a preferred ratio ofmaleinized polyethylene to bitumen is from about 0. 05 to about 10percent by weight, more preferably, from about 0.5 to about 2 percent byweight, and a preferred ratio of amino-functionalized butadiene basedcopolymer is from about 0.01 wt. % to about 3 wt. %, more preferablyabout 0.05 to about 2 wt. % The amount of liquid butadiene may be.preferably in the range of about 0.02 to about 15 wt. %, more preferablyfrom about 0. 1 to about 6 wt. %, of bitumen. The amount of sulfur ispreferably between about 0.05 percent and about 10 percent of the totalmixture, by weight, preferably about 0.1 to about 5 wt. %. For otherapplication, for example, roofing, the relative proportions and totalamounts of components may vary.

Paving materials generally include aggregate, such as crushed stonepebbles and sand, along with the bitumen composition. Similarly, otheradditives to the bitumen composition may be employed, dependent on theend use to which the bituminous composition is put. For example, aroofing material may be obtained by the addition of suitable fillers,such as asbestos, carbonates, silica, wood fibres, mica, sulfates,clays, pigments and/or fire retardants, such as chlorinated waxes. Forcrack-filler applications, an oxide may be advantageously added.

EXAMPLES

In the Examples which follow, the stability of the polymer modifiedbinders during hot storage was evaluated based on (i) the results ofobservation under an optical microscope equipped with temperaturecontrolled hot stage to observe the difference in morphology of samples,and/or (ii) separation testing of conditioned asphalt samples. Theconditioning procedure consists of placing approximately 50 grams ofpolymer-asphalt binder in 2 cm (3/4") copper tubes and storing suchtubes in a vertical position at 160° C. in an oven for 2 to 3 days.Following hot storage a viscosity ratio was determined by comparing theviscosity of the binder from the top section of the tube with the binderfrom the bottom section of the tube. Ratios in the range of 0.80 to 1.20are generally considered indicative of acceptable stability.

Example 1

This Example illustrates the incorporation of copolymeric materials intobitumen compositions.

Compositions were prepared by a two-step procedure, in which aconcentrate first was formed and then the concentrate was diluted withasphalt and adding, while stirring, polymer to be stabilized. In thisExample, the asphalt employed was Lloydminster, Penetration 85/100.

The concentrate was prepared by dispersing functionalized polyethylene(Fusabond E-110, MI=40, anhydride content: 0.08 g mole/Kg of resin) inasphalt at 170° C. for 10 minutes, adding a mixture of amine-terminatedpoly(butadiene-co-acrylonitrile) copolymer (liquid, acrylonitrilecontent 10%, amine equiv. at 1200) and polybutadiene (Ricon 134,MW=12,000) while mixing for 15 minutes at 180° C., and adding sulfurwhile mixing the asphalt for 1.5 hours at 190° C. to 200° C. Theresulting concentrate then was diluted with the same asphalt to form ahomogenous binder to which was added polyethylene (PE) (low density,melt flow index=5) to be stabilized.

Various polymers then were added to the resulting composition in thefollowing manner:

SBS (S:B=30/70, MW=350,000, Mn=140,000): disperse SBS in asphaltcomposition 190° C. for 30 minutes and at 200° to 240° C. for a further30 minutes.

EVA (Cil 1240A, VA=12% by weight, melt flow index=10): disperse EVA inasphalt composition at 180° C. for 30 minutes.

EPDM (Royalene 552, EP ratio 75/25, Morney viscosity ML 1+4 at 125°C.=50): disperse EPDM in asphalt composition at 200° C. for one hour.

EP/PP (recycled diaper waste-PE/PP ratio 60:40 (comingled blend):disperse EP/PP in asphalt composition at 170° C. for 1 hour

Mixing in all Examples was effected in a Brinkman Polytronhomogenizer(Model PT45/80) mixer.

Details of the compositions formed in a series of experiments are setforth in Table I below. In these various experiments, the "c"experiments are control experiments, the "a" experiments are examples ofcompositions according to the present invention and the "b" experimentsare examples of compositions according to WO 93/07219.

The various samples were subjected to testing and the results obtainedare set forth in Table II below. As may be seen from these results, theSBS was processed under conditions in which it was relatively stablyintroduced to the asphalt (Experiment 1(c)) and the presence of thestabilizer alone (Experiment 1(b)) and stabilizer and polyethylene(Experiment 1(a)) did not adversely affect such stability.

In the case of EVA, in the absence of stabilizer, the copolymer readilycoalesced and separated from the asphalt (Experiment 2(c)). Withstabilizer alone (Experiment 2(b)) and stabilizer and polyethylene(Experiment 2(a)), the EVA was stably incorporated into the compositionand did not tend to coalesce or separate from the asphalt, as evidencedby visual observation and as can be seen from the viscosity ratiofollowing conditioning. For EPDM, similar results were obtained as forEVA. The EPDM was more difficult to disperse in the asphalt than EVA,and hence the conditions employed for dispersion were slightly modified.In the case of the comingled blend of EP/PP (60:40 with about 1.0%TiO₂), the blend was stably incorporated into the bitumen (Experiment4(a)) while, in the absence of stabilizer, the dispersed polymers (PEand PP) rapidly coalesced when agitation was stopped.

Example 2

This Example illustrates the addition of polyethylene and SBS tounmodified asphalt.

In a 1 liter mixing vessel, 92 parts of asphalt (Caltex Class 170,penetration at 25° C.=85 dmm, Viscosity at 135° C.=0.32 pa.s., Ring andBall Softening point=45° C.) were heated to 180° C. Then, 5 parts ofpolyethylene (PE, low density, melt flow index=5) and 3 parts ofstyrene-butadiene-styrene (SBS S:B-30/70, Mw=350,000, Mn=140,000) wereadded respectively and dispersed into the hot liquid asphalt for 60minutes. After mixing was stopped, the PE dispersed droplets and SESdispersed phase rapidly coalesced respectively in the hot liquidasphalt. Both PE and SES migrated towards the surface of the liquidasphalt during 24 hr hot storage at 180° C. to form a viscous polymerlayer. This lack of stability against gross phase separation is typicalof polyolefin and styrenic copolymer dispersions in hot liquid asphalt.Polyethylene and SBS tend to coalesce without any synergistic assistanceto each other to prevent such phase separation.

Example 3

This Example comprises Examples A-1, A-2 and A-3, B-1 and B-2 (TableIII), and illustrates the results obtained when SBS is incorporated intoasphalt under different processing conditions. As may be seen from theresults below, at equivalent levels of SBS and PE, vastly differingresults can be obtained.

Example A-1

0.5 part of maleinized polyethylene was dispersed in 18.2 parts ofasphalt (Caltex Class 170) at about 170° C. for 10 min. Following this,0.7 part of polybutadiene and 0.4 part of an amine terminatedpoly(butadiene-co-acrylonitrile) copolymer (ATBN) were added and mixedat around 180° C. for 25 mins, then, 0.6 part of sulfur was blended infor 15 min. To this stirred mixture, was added 71.7 parts of asphalt fordilution and further mixing for 50 min. Finally, recycled low densitypolyethylene (RLDPE) and SBS elastomers were added in sequence and mixedunder high shear at about 200° C. for 35 min (for RLDPE) and for 25 min(for SBS) respectively, forming a bituminous composition wherein polymercomponents were stabilized against phase separation. The performance wasevaluated and shown in Table III.

Example A-2

The procedure of Example A-2 was repeated with a different sequence ofaddition of the additives to asphalt to form the same final compositionwith a controlled mixing time of 160 min. Using the same materials as inExample A-1,0.5 part of maleinized polyethylene, 0.7 part of thepolybutadiene and 0.4 part of the amine terminatedpoly(butadiene-co-acrylonitrile) copolymer were dispersed in 18.2 partsof asphalt for 35 min. 0.2 part of sulfur was added to the mixture andmixed at about 190° C. for 40 min. Then, 71.7 parts of asphalt was addedfor 5 min. dilution. After that, 5 parts of RLDPE with 0.4 part ofsulfur was added and dispersed at around 200° C. for 60 min. followed bythe addition and mixing of 3 parts of SBS for further 20 min to obtain astabilized bituminous composition. The evaluation result was shown inTable III.

Example A-3

Using the same materials as in Example A-1, after 0.5 part of themaleinized polyethylene, 0.7 part of the polybutadiene and 0.4 part ofthe amine functionalized poly(butadiene-co-acrylonitrile) copolymer weredispersed in 18.2 parts of asphalt for 35 min, 74.7 parts of asphaltwhich had been preblended with 4% of SBS at around 180° C. for 30 min.was used to dilute the mixture for 5 min. Then, 0.6 part of sulfur wasadded and reacted at about 200° C. for 70 min and 3 parts of RLDPE wasmixed into the mixture for further 20 min to produce a stabilizedpolymer-bitumen composition. The evaluation on this product is given inTable III.

Example B-1

Using the same materials as in Example A-1, asphalt (92.5% by wt) waspreblended with the maleinized polyethylene (2.5% by wt), thepolybutadiene (3.7% by wt) and amine terminatedpoly(butadiene-co-acrylonitrile) (1.3% by wt) copolymer at around 180°C. for 40 min. The preblend was added, while stirring, to the sameamount of asphalt which had been treated with 3% by weight of sulfur.Then, 20.2 parts of the resultant mixture was diluted with 71.8 parts ofasphalt for 10 min. Finally, 5 parts of RLDPE and 3 parts of SBS wereadded in order and dispersed at about 185° C. for 60 min to produce astabilized polymer-bitumen composition. The evaluation result is shownin Table III.

Example B-2

Using the same materials as in Example B-1, 10.1 parts of the preblendwas mixed with the same amount (10.1 parts) of asphalt which had beentreated with 4% (by wt) of sulfur, then the mixture was diluted andmixed with 71.8 parts of asphalt for 5 min. Finally, 5 parts of RLDPEfollowed by 3 parts of SBS was added and dispersed under a high shearfor 120 min at about 190° C., to produce a stabilized polymer-bitumencomposition.

SUMMARY OF DISCLOSURE

In summary of this disclosure, the present invention provides modifiedstabilized bituminous compositions in which copolymers and/orhomopolymers are stably incorporated to modify the properties of thebitumen composition. Modifications are possible within the scope of thisinvention.

                                      TABLE I                                     __________________________________________________________________________             designation                                                                                            Comingled                                            SBS     EVA     EPDM     PE/PP                                       Ingredient phr                                                                         1a 1b 1c                                                                              2a 2b 2c                                                                              3a 3b 3c 4a 4c                                       __________________________________________________________________________    SBS      2  2   2                                                                              -- -- --                                                                              -- -- --                                             EVA      -- -- --                                                                              2  2   2                                                                              -- -- --                                             EPDM     -- -- --                                                                              -- -- --                                                                              2  2  2                                              PE/PP    -- -- --                                                                              -- -- --                                                                              -- -- -- 3   3                                       PE       2  -- --                                                                              2  -- --                                                                              2  -- --                                             AC-Lloyd-minster                                                                       94.4                                                                             86.36                                                                            98                                                                              92.80                                                                            94.73                                                                            98                                                                              92.80                                                                            94.73                                                                            98.0                                                                             94.6                                                                             97                                       85/100                                                                        FPE      0.48                                                                             0.49                                                                             --                                                                              0.96                                                                             0.98                                                                             --                                                                              0.96                                                                             0.98                                                                             -- 0.7                                                                              --                                       ATBN     0.32                                                                             0.33                                                                             --                                                                              0.64                                                                             0.65                                                                             --                                                                              0.64                                                                             0.65                                                                             -- 0.5                                                                              --                                       LPBD     0.64                                                                             0.65                                                                             --                                                                              1.28                                                                             1.31                                                                             --                                                                              1.28                                                                             1.31                                                                             -- 1.0                                                                              --                                       Sulfur   0.16                                                                             0.17                                                                             --                                                                              0.32                                                                             0.33                                                                             --                                                                              0.32                                                                             0.33                                                                             -- 0.2                                                                              --                                       __________________________________________________________________________

                                      TABLE II                                    __________________________________________________________________________                                         SAMPLE AFTER STORAGE                                                               Viscosity                                                                             Viscosity                                SAMPLE BEFORE STORAGE   Storage                                                                            at top  at bottom                                                                            Viscosity                         Penetration                                                                            Viscosity                                                                             S.P.   Period                                                                             (V.sub.t)                                                                             (V.sub.b)                                                                            Ratio                SAMPLES                                                                              Copolymer                                                                           (dmm @ 25° C.)                                                                  (cp @ 135° C.)                                                                 (R&B ° C.)                                                                    (hrs)                                                                              (cp @ 135° C.)                                                                 (cp @ 135°                                                                    (V.sub.t                                                                      /V.sub.b)            __________________________________________________________________________    control      90        550    45                                              1a     SBS   47       3650    63     48   4600    4800   0.96                 1b     SBS   43       2750    65     48   2025    2075   0.98                 1c     SBS   67       1900    59     48   1550    1550   1.00                 2a     EVA   62       3100    58     72   2700    2785   0.97                 2b     EVA   65       2400    56     72   1875    1925   0.97                 2c     EVA   74       1000    52     72   1550     825   1.88                 3a     EPDM  59       4225    59     48   3550    3650   0.97                 3b     EPDM  55       2600    52     48   2225    2225   1.00                 3c     EPDM  73        950    50     48   1250     750   1.60                 4a     PE/PP 70       2025    55     48   1900    1700   1.12                 4c     PE/PP 65       1050    54     48   1075     800   1.34                 __________________________________________________________________________

                  TABLE III                                                       ______________________________________                                                  Example 2                                                                     Group A     Group B                                                 Component, phr                                                                            A-1    A-2    A-3   B-1   B-2                                     ______________________________________                                        Asphalt     89.9   89.9   89.9  90.7  90.7                                    Fusabond E-110                                                                            0.5    0.5    0.5   0.3   0.3                                     LPBD        0.7    0.7    0.7   0.4   0.4                                     ATBN        0.4    0.4    0.4   0.3   0.3                                     Sulfur      0.6    0.6    0.6   0.3   0.4                                     SBS         3.0    3.0    3.0   3.0   3.0                                     PE          5.0    5.0    5.0   5.0   5.0                                     Performance                                                                   Penetration 40     38     26    23    5                                       dmm at 25° C.                                                          Torsoral    --     --     --    9     --*                                     Recovery % at 25° C.                                                   Viscosity   9.4    7.5    11.4  3.75  4.4#                                    Pa.s. at 135° C.                                                       Softening Point                                                                           74     77     75    67.3  91.5                                    (R&B) (° C.)                                                           Elastic Recovery                                                                          --     --     --    11.3  53.6                                    Pa.s. at 60° C.                                                        Viscosity   --     --     --    5,055 181,900                                 Pa.s. at 60° C.                                                        ______________________________________                                         *too rigid at 25° C. to be tested.                                     # = test at 165° C.                                               

What is claimed is:
 1. A bituminous composition comprising:bitumen, atleast one first polyolefin sterically stabilized in dispersedparticulate form in the bitumen by a bicompatible molecule comprising abitumen-compatible polymer interlinked with a second polyolefin, saidsecond polyolefin being bonded to said at least one first polyolefin,and at least one additional elastomeric polymeric material which is astyrenic copolymer or an olefinic copolymer and which is stablyincorporated into the bitumen by entanglement, physical entrapment,chemical cross-linking or a combination of two or more of suchmechanisms.
 2. The composition of claim 1 wherein said at least onefirst polyolefin is polyethylene.
 3. The composition of claim 1 whereinsaid styrenic copolymer is an SBR, SBS, SEBS, or SIS copolymer.
 4. Thecomposition of claim 1 wherein said olefinic copolymer is an EVA, EMA,EPDM or polypropylene copolymer.
 5. The composition of claim 2 whereinsaid polyethylene is present in said composition in an amount of fromabout 0.5 to about 20 wt. % and said elastomeric copolymer is present insaid composition in an amount of from about 0.5 to about 20 wt. %.
 6. Amethod of forming a bituminous composition, which comprises:dissolving afunctionalized butadiene polymer having a first functional group at oneend thereof and which is compatible with bitumen in a solvent which isbitumen or an oil soluble in bitumen, dispersing in said solvent afunctionalized polyolefin having a second functional group at one endthereof capable of reacting with the first functional group, reactingsaid first and second functional groups so as to bind the one end ofsaid functionalized polyolefin to the one end of said polybutadienepolymer to form a bicompatible molecule having a free polyolefinic end,dispersing a polyolefin in a molten particulate form in said solvent toprovide in the bituminous composition, steric stabilization of saidparticulate polyolefin by bonding of the free polyolefinic end of thebicompatible molecule to said particulate polyolefin, dispersing atleast one additional, elastomeric polymer which is a styrenic or anolefinic copolymer in said solvent to provide, in the bituminouscomposition, stable incorporation of the at least one additional polymerby entanglement, physical entrapment, chemical cross-linking or acombination of two or more of such mechanisms, and where said solvent isoil soluble in bitumen, dispersing the resultant composition in bitumen.7. The method of claim 6 wherein said styrenic copolymer is an SBR, SBS,SEBS, or SIS copolymer.
 8. The method of claim 6 wherein said olefiniccopolymer is an EVA, EMA, EPDM or polypropylene copolymer.
 9. The methodof claim 6 wherein said dispersed particulate polyolefin is polyethylenewhich is present in said composition in an amount of from about 0.5 toabout 20 wt. % and said additional elastomeric copolymer is present insaid composition in an amount of from about 0.5 to about 20 wt. %. 10.The method of claim 6 wherein said additional, elastomeric copolymer isan SBS or SBR copolymer present in an amount of about 1 to about 15 wt.%.